<?php

    /**
     * PHPExcel_CalcEngine_CyclicReferenceStack
     * Copyright (c) 2006 - 2015 PHPExcel
     * This library is free software; you can redistribute it and/or
     * modify it under the terms of the GNU Lesser General Public
     * License as published by the Free Software Foundation; either
     * version 2.1 of the License, or (at your option) any later version.
     * This library is distributed in the hope that it will be useful,
     * but WITHOUT ANY WARRANTY; without even the implied warranty of
     * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
     * Lesser General Public License for more details.
     * You should have received a copy of the GNU Lesser General Public
     * License along with this library; if not, write to the Free Software
     * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
     * @category   PHPExcel
     * @package    PHPExcel_Calculation
     * @copyright  Copyright (c) 2006 - 2015 PHPExcel (http://www.codeplex.com/PHPExcel)
     * @license    http://www.gnu.org/licenses/old-licenses/lgpl-2.1.txt    LGPL
     * @version    ##VERSION##, ##DATE##
     */
    class PHPExcel_CalcEngine_CyclicReferenceStack {
        /**
         *  The call stack for calculated cells
         * @var mixed[]
         */
        private $stack = [];

        /**
         * Return the number of entries on the stack
         * @return  integer
         */
        public function count() {
            return count($this->stack);
        }

        /**
         * Push a new entry onto the stack
         * @param  mixed $value
         */
        public function push($value) {
            $this->stack[$value] = $value;
        }

        /**
         * Pop the last entry from the stack
         * @return  mixed
         */
        public function pop() {
            return array_pop($this->stack);
        }

        /**
         * Test to see if a specified entry exists on the stack
         * @param  mixed $value The value to test
         */
        public function onStack($value) {
            return isset($this->stack[$value]);
        }

        /**
         * Clear the stack
         */
        public function clear() {
            $this->stack = [];
        }

        /**
         * Return an array of all entries on the stack
         * @return  mixed[]
         */
        public function showStack() {
            return $this->stack;
        }
    }
